Magnetic impact generator base fuze



July 7, 1959 e. N. WIENOLD ET AL ,8

MAGNETIC IMPACT GENERATOR BASE FUZE Filed June so, 1955 INVENTORS GEORGE N. WIENOLD 4 Sheets-Sheet 1 GEORGE S. PFEIFFER DONALD E. HE

R7IZNSON av V AITT'YG July 7, 1959 GQN. WIENOLD ET AL MAGNETIC IMPACT GENERATOR BASE FUZE Filed June so, 1955 4 Sheets-Sheet 2 Q :0 N SLRO |Y mm? T mmw .A E EM w N W ES. 7+ NE 0 D EWL G A N O D W. BV/

e. N. WIENOLD ET AL 2,893,321

MAGNETIC IMPACT GENERATOR BASE FUZE July 7, 1959 4 Sheets-Sheet I5 Filed June 30, 1955 W Y Mm D R m T o A T T A NWW W5; 7 mmw N EE GGM R R OO EE G G D Y B July 7, 1959 G. N. WIENOLD ET AL 2,893,321

7 MAGNETIC IMPACT GENERATOR BASE FUZE Y Filed June 30, 1955 4 Sheets-Sheet 4 VENTORSZ.

IN GEORGE N. WIENOLD GEORG PF FER DQNALD E.HE ANSON ATT'Y MAGNETIC DVIPACT GENERATOR BASE FUZE George N. Wienold and George ..'Pfeli fer, Chicago, and

Donald E. Hermanson, Palatine, 'I]l., as'signor's to Stewart-Warner Corporation, Chicago, 111., a corporation of Virginia Application June 30, 1955, Serial No. 519,054 '5 Clainis. (c1. maine The invention relates generally to projectiles and more particularly to safe, automatic means for arming the fuze of a rifle projectile to condition the projectile for detonation.

In the past it has been more or less conventional to provide either centrifugal means responsive to the rotation of the projectile to arm the fuze after a predetermined rotational speed of the projectile has been attained, or to provide means responsive to the inertia due to linear acceleration of the projectile (the setback force), to arm the projectile.

It is an object of the invention to improve the means for automatically arming the fuze and detonator in response to the rotation and angular acceleration of the projectile, and further to provide additional safety means for attaining delayed arming. g

It is therefore the rimary object at the invention to provide an improved fuze in 'whic'h the arming is delayed for a predetermined interval after the projectile or shell has been projected from the muzzleof the rifle.

A further object is to provide an electrical generator for fuzes of projectiles, which is superior in energy output and sensitivity, to insure detonation upon impact with an object providing relatively small inertial resistance.

A further object is to provide an improved electricalcircuit for guaranteeing low resistancecontinuity together with means for breaking a shunt. circuit, thereby to render an electric igniter or primer susceptible to be energized by an electrical generator, to initiate detonation of the projectile upon impact. 7

Other objects will appear from the following description, reference being had to the accompanying. drawings in which:

Fig. 1 is an enlarged transverse cross-sectional view of a fuze incorporating our invention, taken on the line 1-1 of Fig. 2;

Fig. 2 is a diametral central cross-sectional. view taken on the line 2-2 of Fig. 1.; A I g V Fig. 3 is a. cross-sectional view taken on the line 3-3 of Fig. 4; u

Fig. 4 is a transverse sectional view taken on the line 44 of Fig. 3; v

Fig. 5 is a fragmentary cross-sectional view taken on the line 5-5 of Fig. 1; p

Fig. 6 is a blowup of. a portion of the section shown in Fig. 5; I

Fig. 7 is a transverse sectional view taken on. the line 7-7 of Fig. 3; I

Fig. 8 is a fragmentary sectional view taken on the line 8-8 of Fig. 7;

Fig. 9 is a transverse sectional view taken on: the line 9-9 of Fig. 3;

Fig. 10 is a diagrammatic view to illustrate the operation of the fuze arming apparatus, viewed from the nose of the projectile;

Fig. 11 is a schematic circuit diagramofthe-electrical means for arming the fuze; and

Fig. 12 is a fragmentary sectional view showing a 2 centrifugally operated detent, its mounting, and its return spring. Y p

In general, the fuze of the invention comprises means for delaying the arming in response to the initial angu lar acceleration of the projectile as it is being propelled throughthe bore of a rifle, and, after the projectile leaves'the muzzle of the rifle, providing timing means for delaying the complete arming of the fuze; and, in addition, to provide a very sensitive means for causing detonation upon impact. The means for accomplishing these functi'ons are so constructed and arranged that complete safety during handling of the shell is assured.

As best shown in Figs. 1 and 2, the fuze mechanism comprises a closed end cylindrical body 20 which is provided with threads 22 for securing it in the base, or breech end, of a projectile. Within the body 20 of the fuze is secured a booster charge 24 of tetryl, or the like, confined within a booster screw cap 26 threaded in the body 20. To insure against the entrance of moisture into the charges within the fuze body, the booster screw cap 26 is provided with an annular groove 28 which is filled through an aperture 30 with a suitable sealing alloy which expands upon congealing, such as an alloy containing bismuth.

The explosion of the booster charge 24 is caused by the initiation of detonation in a booster lead-in charge 32' contained in a booster lead-in cup 34 having a press fit within a rotor housing 36.

The rotor housing 36 is covered by two sealing layers (as best shown in Fig. 6), one layer 40 or paper or similar fabric material, and another layer 38 of a suitable metal foil such as aluminum foil. These layers 40 and 38 are compressed against the rotor housing 36 by the booster enclosing screw cap 26 to prevent piemature leakage of gases from the primer and detonator'.

A rotor 42 is mounted within the rotor housing 36 on an anti-friction bearing 44, the spindle 46 of which is die cast as an insert in a rotor support 48, the latter being non-rotatably supported by' a generator housing 50, preferably made of suitable phenolic plastic composition. 7

As best shown in Fig. 3, the generator housing 50' encloses an impact-operated electrical generator coinpris'in'g an armature or pole 52, made are suitable ferromagnetic material such as soft iron, having a down- Wardl'y projecting part secured by a press fitin a sleeve 54 of nonmagnetic material, such as aluminum, and to asurrounding annulus 56 made of a metal of high magnetic retentivity, such as Alnico.

The armature assembly 52, 54, and 56 is guidedby, and slidable in, a sleeve 58 of nonmagnetic material, such as brass. The armature assembly normally rests in contact with the central and peripheral portionsof a field housing 60 in which is fixed a generator coil 62. It will be understood that, upon impact, the armature assembly 52, 54 and 56, due to its momentum, will move forwardly (with respect to the coil and housing. assembly-in the direction of flight), and, due to the rapid reduction of the magnetic flux induced by its leaving the housing and coil assembly will generate a substantial current in the coil 62. The rapidity of change in magnetic flux density through the coil is enhanced by thefact that the lower surface of the magnet 56 is conically concave.

The particular construction of this electrical generator is of importance in that, upon impact, it produces maximum energy output in minimum time when the projectile strikes low resistance targets. v

The armature assembly 52, 54-, and 56, in moving through a relatively small portion of its (approximately total travel, generates in the coil 62 sufficient energy to assure heating an electrical igniter to a temperature which will without fail cause ignition of a detonating charge, as will appear more fully hereinafter. The means for detonating the charge upon impact has been described in general. The following is a description of the means for arming the fuze a predetermined time interval after the projectile leaves the muzzle of the rifle.

As best shown in Fig. 4, the rotor 42, which as previously indicated, is mounted for free rotation on anti-friction bearing 44, has a pair of interlock notches 68 in which a pair of detents 70 normally rest. In Fig. 4 the detents 70 are shown in the position they assume upon the attainment of a predetermined rotational velocity. Initially, after the rotor 42 has rotated clockwise (Fig. 4) relative to the body of the fuze sufficiently to permit the detents to swing outwardly from their interlock notches 68, due to the camming action of the rotor 42 resulting from its inertia lag as it rotates clockwise (Fig. 4) relative to the body of the fuze, and further due to the centrifugal force acting upon the detents 70, these detents will move to the position shown in Fig. 4. This position of the detents 70 is that normally attained as the projectile is impelled through the bore of the rifle, and is usually maintained throughout the projectiles flight. The outward swinging movement of the detents 70 is resisted by torsion coil springs 72 (Figs. 3 and 12) surrounding headed pivot pins 74 pressed into the rotor support 48.

In addition to the detents 70 co-operating with the interlock notches 68, means are provided for preventing complete rotation of the rotor 42 relative to its housing 36 in the form of a third detent 76 (Fig. 4) which, urged by a torsion spring 78, normally lies in the path of a cleaver pin 80 which is press-fitted in the rotor 42.

From the schematic circuit diagram of Fig. 11 it will be observed that the coil 62 is adapted to supply energizing current to an electrical igniter 82 which comprises a part of a primer 84. This primer, as previously stated, may comprise a suitable primer explosive mixture. However, normally the generator coil 62 is short-circuited by a low resistance bridge wire 86 which is connected between terminal posts 88 and 89 which are connected to the output terminals 108, 109 of the generator. The resistance wire 82 is matched with the impedance of generator coil 62 to attain maximum energy output.

The manner in which the fuze is armed by severing the bridge wire 86 will now be described.

As the projectile acquires angular momentum in the bore of the rifle, the detents 70 are cammed outwardly, due to the lag of the rotor 42, and moved further, by centifrugal force, into the position in which these detents are shown in Fig. 4.

Referring now to Figs. 2 and 10, the rotor 42 includes a detonator 92 which, when the fuze is assembled, is positioned as indicated in full lines in Fig. 10.

Fig. is a diagrammatic view of the projectile as viewed from the nose. Normally naval and artillery pieces are rifled so as to impart clockwise rotation to the projectile as viewed from the breech, or counter-clockwise as viewed in Fig. 10. In Fig. 10 the rotor 42 is, therefore, indicated by the arrows 94 as having an initial clockwise movement imparted thereto, due to its inertia, with respect to the surrounding projectile. The torque resulting from this inertia efiect is resisted by a coil spring 96 (Fig. 3), the lower end of which is suitably secured to the spindle 46 and the upper end of which has a radially extending tang which is secured to the rotor 42 by clenching cleats 98 (Fig. 1).

(As the projectile is accelerated, the detents 70 are initially cammed radially outwardly by the rotor 42 and thereafter are moved to the positions shown in Fig. 4 by centrifugal force so that the rotor and a detonator 92 carried thereby are moved clockwise (as shown by arrows 94 in Fig. 10), through an angle of approximately 90. It is arrested in this position by the abutment of the cleaver pin 80 with the end of an arcuate groove 95 (Fig. 9) formed in the top of the rotor support 48.

Thereafter, as the projectile leaves the muzzle of the rifle and it no longer is being angularly accelerated, the spring 96 acts upon the rotor 42 to return it counterclockwise through an angle of 270, as indicated by the arrows 100.

Additional safety means are'provided to prevent accidental detonation. If, for example, for some reason, during shippingor handling, the detents 70 should have disengaged accidentally from the rotor 42 and permitted the spring .96 to rotate the rotor 42 counterclockwise, the detent .76 would, through engagement with the cleaver pin 80, prevent counterclockwise movement of the rotor to the full 270 position (Fig. 10) and thereby prevent alignment of the detonator 92 with the primer 84 and the booster lead-in v32. Thus, if the bridge wire 86 should have been broken accidentally, and should the primer 84 thereupon be ignited, detonation will nevertheless not take place, due to misalignment of the explosive relay, or detonator, 92 with the primer 84 and with the lead-in charge 32. In other words, the rotor 42 and the detonator 92 will move to the position indicated at 92a (Fig. 10), in a safety position, not quite in alignment with the booster lead-in 32 and primer 84.

As indicated in Fig.10, failure of operation of the detents 70 will result in the stoppage of counterclockwise rotation of the rotor 42 by the detent 76 after the rotor has rotated counterclockwise 228 (Fig. 10). However, assuming that the detents 70 and 76 have operated in a normal manner, the rotor will continue rotation to the 247.5 position of Fig. 10, whereupon the cleaver pin 80, by means of its downwardly extending cutting blade 106, will shear the bridge wire 86.

In normal operation, as the rotor 42 is rotated by the spring 96 to the 270 position indicated in Fig. 10, a spring-pressed plunger 102 (Fig. 5) carried by the rotor is projected into a bore 104 in the rotor housing 36 to lock the rotor in its fully armed position, to prevent any possible rebound of the rotor.

It will be noted that the bridge wire 86 is connected between a pair of terminal posts 88 and 89 which are connected to the output terminals 108, 109 (Figs 7 and 11) of the generator coil 62, being held swaged in diametral slots formed therein.

The terminals 88 and 89 are connected by wires 107 to terminal posts 108 and 109, respectively (Figs. 7 and 11), which are preferably inserts in the molded generator housing 50. Each of these terminal posts has diametral cross-slots to receive the ends of conductors to be joined, and has an initially frustoconical end portion for convenience in applying a swaging tool by which the portions of the terminals adjacent the slots are brought together, thereby securing clamping the wire ends in the slots, assuring good mechanical and electrical connections. As a probably unnecessary precaution, soldering or welding may be employed.

Wires 111 connect the terminal posts 108 and 109 to the electrical igniter 82. The terminal posts are prevented from coming into contact with the fuze body 20 by an insulating disc 116 (Figs. 2 and 8).

The generator housing 50 is held from rotation in the fuze body 20 by a pin 118 (Fig. 2) inserted in the housing and projecting into a closed end hole in the fuze body, and the rotor support 48 has a non-cylindrical surface engaging a complementary surface of the housing 50 so that the support 48 will likewise not rotate relative to the fuze body 20.

In use the fuze has many advantages. The pawls 70 are pivoted at diametrically opposite points so that ii the fuze is subjected to shock in handling only onc of the pawls could conceivably be jarred from its rotor-locking position. The pawls 70 are held in their notches 68 in rotor 42, not only by their individual springs 72 but also by the spring 96, which holds the rotor in a position such that the pawls cannot'swing outwardly, due to the interlocking grooves 68. v

For economy in production, the parts 36, 42 and 48 are preferably die casts while the generator housing 50 is preferably a molded plastic. The provision of the aluminum sleeve 54 makes unnecessary costly machine operations to fit the permanent magnet 56 to the permeable armature 52. The sleeve 54 is staked and expanded between the permanent magnet 56 and the armature 52, as indicated in Fig. 3. The permanent magnet 56 is preferably made of a pressed and sintered alloy of high magnetic retentivity. The core 60 is preferably made of a pressed and sintered iron of high permeability.

The shape of the permanent magnet 56 is of significance in that only the central portion of the armature 52 and the extreme peripheral edged portion of the permanent magnet 56 are in the magnetic flux path so that, upon impact, there is a rapid change in flux density passing through the coil 62 with the result that a high energy pulse is produced upon impact with the relatively fragile target. The sensitivity of the fuze, for explosion on impact, is therefore greatly enhanced.

By virtue of the delayed arming which can be accomplished only by rapid acceleration of the projectile through the bore of the rifle, and because of the fact that the detents 70 are held outwardly by centrifugal force, and further because of the use of the cleaver pin which severs a circuit shunting the generator, the projectile embodying a fuze of this invention is very safe to handle and cannot conceivably explode permaturely, and thus is extremely safe for personnel handling it and for equipment; that is, the rifle through which it is projected and other materiel adjacent thereto. The fuze above indicated is highly sensitive to impact, but such sensitivity is secured only after the projectile in which the fuze is contained has been angularly accelerated and after it has continued to rotate on its axis for a predetermined length of time. Yawing and other erratic movement of the projectile does not have any efiect upon the arming mechanism.

While we have shown and described a preferred embodiment of our invention, it will be apparent that variations and modifications thereof may be made without departing from the principles and scope of the invention. We therefore desire, by the following claims, to include all such variations and modifications by which substantially the results of our invention may be obtained through the use of substantially the same or equivalent means.

We claim:

1. A mechanism for arming the fuze of a projectile comprising a body, a rotor mounted for rotation relative to said body on substantially the longitudinal axis of the projectile, resilient means between the rotor and the body biasing the rotor against rotation in response to its inertia as the projectile is angularly accelerated in the bore of the rifle, detent means normally engaging the rotor to hold it against rotation by the resilient means, said detent means being mounted for outwardly swinging movement in response to centrifugal force and having resilient means biasing the detent means into engagement with the rotor, stop means to limit the extent of rotary movement of the rotor in response to the force applied thereto by said resilient means, an electrically ignited primer and a booster lead-in charge mounted in alignment in the body, a detonator charge in the rotor positioned to be in alignment with the primer and booster lead-in charge when the rotor is arrested by said stop means, an impact operated electri cal generator connected to said primer, a bridge connector normally short circuiting the output of the generator, and means carried by the rotor to sever the bridge connector shortly before the rotor moves to the position in which it is arrested by said stop means.

2. A mechanism for arming the fuze of a projectile comprising a body, a rotor mounted for rotation relative to said body in one direction in response to angular acceleration of the projectile, resilient means connected between the rotor and the body biasing the rotor to rotate in the opposite direction, cam means on the rotor, detent means normally engaging the rotor to hold it against rotation by the resilient means, said detent means normally engaging the cam means and being mounted to be cammed outwardly by the rotor as it rotates in the first direction, and to swing further outwardly in response to centrifugal force, resilient means biasing the detent means into engagement with the rotor, stop means to limit the extent of rotary movement of the rotor in response to the force applied thereto by said resilient means, an electrically ignited primer and a booster lead-in charge mounted in alignment in the body, a detonator charge in the rotor positioned to be in alignment with the primer and booster lead-in charges when the rotor is arrested by said stop means, and means to cause ignition of the primer upon impact of the projectile with the target.

3. A base fuze mechanism for a rifle projectile, comprising, a body, a rotor mounted for rotation in one direction in the body in response to angular acceleration of the body, resilient means to rotate the rotor in the opposite direction, a stop to limit the extent of rotation of the rotor in the latter direction, explosive charges in the rotor and in the body brought into alignment with one another only when the rotor is in the position in which it is arrested by the stop, an impact operated electrical generator having output terminals, an electrical igniter for one of the explosive charges in the body connected to the generator output terminals, a shunt circuit connected to the output terminals of the generator, and means carried by the rotor to open the shunt circuit as the rotor closely approaches the position in which it is arrested by said stop.

4. In a base fuze mechanism for a rifle projectile; the combination of a generator coil; a permanently magnetized armature cooperable with said coil and movable with respect thereto in response to its inertia upon impact of the projectile with a target; low resistance circuit means normally shunting the output of the generator; an electrical charge igniting means connected to the output of the generator; and means, rendered operative by a predetermined extent of angular acceleration of the projectile as it advances through the bore of the rifle and operable to break the shunting circuit means a predetermined time interval after the projectile is projected from the bore of the rifle and is no longer angularly accelerated.

5. In a base fuze mechanism, the combination of a body adapted to be secured in a projectile, a rotor mounted for rotation within the body on an axis substantially the same as that of the projectile, resilient means biasing the rotor to rotate in a first direction, detent means normally preventing movement of the rotor by the resilient means, said rotor operating upon the detent means to render it inefiective in response to angular acceleration of the projectile, explosive charges in the body and in the rotor, said charges being normally positioned out of alignment with one another, stop means on the rotor and body to limit rotation of the rotor by the resilient means to a position in which the charge on the rotor is in alignment with the charges in the body, normally inefiective means to cause ignition of the charge in the body in response to impact of the projectile with a target, and means operated by the rotor as it approaches the position in which it is stopped by the stop means to render the ignition means effective to operate when the projectile strikes the target.

References Cited in the file of this patent UNITED STATES PATENTS 2,486,362 OBrien Oct. 25, 1949 2,748,704 Dinsmoor June 5, 1956 FOREIGN PATENTS 525.333 Great Britain Aug. 27, 1940 

